Such an electrode array can be used for acute or chronic (i.e., long-time) implantation in humans and/or animals and for recording and/or stimulation, in particular at the cerebral surface of the cortex. Signals recorded with the contact pads of such planar electrodes may be e.g., of the ECoG (Electrocorticography) type.
If, on the other hand, simultaneous recording and/or stimulation in depth of the cortex is additionally required, elongated electrodes (depth electrodes) have to be used which reach into such deeper regions of the cortex. Such elongated electrodes may be placed at the same superficial position of the cortex as the electrode array comprising the planar electrodes. With the small sensing surfaces, the elongate electrodes may be used for recording the activity of single neurons or oscillatory brain activity in the form of local field potentials (LFPs) which represents the activity of a population of neurons in a small volume. The same depth electrodes can also be used for providing micro stimulation to small populations of neurons. Together with planar and elongated contacts, this electrode can simultaneously sense neural activity at various spatial resolutions at the cortical surface and in different layers of the cortex.
Likewise in the peripheral nervous system or the spinal cord, the electrode array is used to record and or stimulate from the surface of the nerve/spinal cord, and the elongated electrodes are used to record/stimulate from within the nerve/spinal cord.